JP5740262B2 - Image sensor module and power supply circuit thereof - Google Patents

Description

  The present invention relates to an image pickup device module and a power supply circuit thereof, and more particularly to an image pickup device module capable of reducing noise in a picked up image signal and a power supply circuit thereof.

  Electronic devices (for example, cellular phones) on which an image sensor module is mounted have been improved in functionality and performance, and the number of mounted components has been increased and the display panel has been increased in size. For this reason, the image pickup device module itself has to be further reduced in size, and the power supply circuit needs to be provided close to the image pickup device (image sensor).

  FIG. 7 is a cross-sectional view illustrating an example of a recent image sensor module. The image sensor module 1 includes an image sensor 2 and a photographing lens group 3 arranged on the light incident side of the image sensor 2. An actuator 4 for focus position adjustment and zoom adjustment is provided in the vicinity of the photographing lens group 3, and power is supplied from the battery power source on the electronic device (device main body) side to the periphery of the image sensor 2. A power supply circuit 5 for generating a voltage for driving the image sensor 2 and the like is provided in the vicinity.

  A switching power supply circuit or the like is used as a power supply circuit that receives power supply from a battery power supply and converts the voltage to generate a predetermined DC constant voltage (for example, 3.3 V). In order to efficiently perform this voltage conversion, an inductor (coil) is used as shown in the circuit diagrams of Patent Documents 1 and 2, for example.

  That is, as shown in FIG. 7, the inductor 6 of the power supply circuit 5 is disposed close to the image sensor 2.

JP 2005-168230 A JP 2005-198484 A

When a current flows through the inductor 6 of the power supply circuit 5, electromagnetic noise 7 is generated as shown in FIG. When the inductor 6 is disposed close to the image sensor 2, electromagnetic noise 7
Enters the image sensor 2.

  In recent years, the image pickup element 2 has been miniaturized because of the increase in the number of pixels, and the amount of signal charge detected by each pixel is reduced according to the amount of incident light. For this reason, even weak electromagnetic noise 7 degrades the image quality of the captured image.

  Conventionally, the distance between the image pickup element 2 and the inductor 6 can be set to a certain extent, and the size of each pixel is not so small, so this weak electromagnetic noise has not been a problem. Therefore, it has become necessary to avoid image quality degradation caused by this electromagnetic noise.

  A power supply circuit that does not generate electromagnetic noise, that is, does not use the inductor 6 suffices to be used. However, this reduces the voltage conversion efficiency and shortens the battery life on the apparatus body side.

  An object of the present invention is to provide an imaging element module capable of capturing a high-quality image while avoiding the influence of electromagnetic noise caused by an inductor, and a power supply circuit thereof.

The power supply circuit of the imaging device module according to the present invention includes a step-down circuit unit that steps down and outputs an input DC voltage using a switching transistor and an inductor, and an input DC voltage that is provided in parallel with the step-down circuit unit by linear constant voltage operation of the transistor. A linear regulator circuit unit that steps down and outputs, a step-up circuit unit that is connected in series to the subsequent stage of the step-down circuit unit and boosts and outputs an input DC voltage by a charge pump operation, and the imaging element module in the shooting recording mode And a control control unit for stopping the operation of the step-down circuit unit and operating the linear regulator circuit unit to supply a constant voltage necessary for driving the image sensor to the image sensor.

  An imaging element module according to the present invention includes the power supply circuit described above.

  According to the present invention, in the operation mode for capturing a high-quality image as in the shooting recording mode, the step-down operation using the inductor is stopped, and instead the step-down operation is performed by operating the linear regulator unit. A high-quality subject image that avoids the influence of electromagnetic noise can be taken.

1 is a circuit diagram of a power supply circuit according to a first embodiment of the present invention. 2 is a flowchart showing an operation procedure of the power supply circuit shown in FIG. 1. It is a circuit diagram of the power supply circuit which concerns on the 2nd Embodiment of this invention. It is a circuit diagram of the power supply circuit which concerns on the 3rd Embodiment of this invention. 5 is a flowchart showing an operation procedure of the power supply circuit shown in FIG. It is a circuit diagram of the power supply circuit which concerns on the 4th Embodiment of this invention. It is sectional drawing which shows an example of an image pick-up element module.

  Hereinafter, an embodiment of the present invention will be described with reference to the drawings.

  FIG. 1 is a circuit diagram of a power supply circuit 5-1 according to the first embodiment of the present invention. The power supply circuit 5-1 of the present embodiment receives power supply from the battery 8 on the apparatus main body side (for example, the mobile phone side), converts the power, and applies, for example, 3.3V to the image sensor 2 (for example, a CMOS image sensor). Supply DC constant voltage.

  The output voltage of the battery 8 changes from a state of about 4.8 V when fully charged to a state where the battery consumption has progressed and the voltage has dropped to about 2.3 V. Since the power supply circuit 5-1 needs to generate a constant voltage of 3.3 V from this changed voltage, the power supply circuit 5-1 is composed of a combination of a booster circuit and a step-down circuit.

  The camera module step-up / down power supply circuit 5-1 of this embodiment is provided in parallel to the step-down switching circuit unit 20 connected to the output line of the battery 8 and the step-down switching circuit unit 20 connected to the output line of the battery 8. The linear regulator circuit unit 30 and the step-down switching circuit unit 20 and the step-up switching circuit unit 40 connected to the output of the linear regulator circuit unit 30 are configured.

  An output capacitor (capacitor) 51 is connected between the output line of the step-up switching circuit unit 40 and the ground, and a predetermined DC constant voltage (3.3 V in the illustrated example) necessary for driving the image sensor 2 is applied to the image sensor. 2 is supplied.

  Error detection resistors 52 and 53 are connected in series between the output terminal of the step-up switching circuit unit 40 and the ground, and a connection point between the resistor 52 and the resistor 53 is connected to one input terminal of the comparator 54. The reference voltage value 55 is input to the other connection end of the comparator 54, and the comparison result of the comparator 54 is input to the mode controller 56.

  The mode control controller 56 selects the circuit units 20, 30, and 40 to be operated, and gives control instructions such as the step-up and step-down levels of the circuit unit to be operated. The detection result of the input voltage detector 57 connected to the eight output lines and a mode switching signal 58 to be described later are input, and based on these, the step-down switching circuit unit 20, the linear regulator circuit unit 30, and the step-up switching circuit unit 40.

  The step-down switching circuit unit 20 includes a buck switching (switching is abbreviated as “SW” in the drawing) controller 21, an NMOS transistor 22, a PMOS transistor 23, and an inductor 6. Performs on / off control (switching control) of the gates of the transistors 22 and 23 based on an instruction from the mode controller 56.

  The source of the PMOS transistor 23 is connected to the output line of the battery 8, the drain of the PMOS transistor 23 and the drain of the NMOS transistor 22 are connected to the input terminal of the inductor 6, and the source of the NMOS transistor 22 is connected to the ground. The output terminal of the inductor 6 becomes an output line of the step-down switching circuit unit 20.

  The linear regulator circuit unit 30 switches the PMOS transistor 31 whose source terminal is connected to the output line of the battery 8, and the gate of the PMOS transistor 31 to the step-down switching circuit unit 20 based on an instruction from the mode control controller 56. And an LDO (low dropout) controller 32 to be controlled. The drain of the PMOS transistor 31 is connected to the output line of the circuit unit 20 (the output line of the inductor 6).

  The step-up switching circuit unit 40 includes two NMOS transistors 41 and 42 connected in series between the output line of the circuit unit 20 (= the input line of the circuit unit 40) and the ground, and the input line and circuit unit of the circuit unit 40. 40, two PMOS transistors 43 and 44 directly connected to the output line 40, a charge capacitor 45 connected between a connection point of the transistors 41 and 42 and a connection point of the transistors 43 and 44, and each transistor A boost (or charge pump) switching controller 46 that performs on / off control of each of the gates 41 to 44 based on an instruction from the mode controller 56 is configured.

  The drain of the NMOS transistor 41 is connected to the input line of the circuit unit 40, the source is connected to the drain of the transistor 42, and the source of the transistor 42 is connected to the ground. The source of the PMOS transistor 43 is connected to the input line of the circuit 40, the drain is connected to the source of the transistor 44, and the drain of the transistor 44 is the output line of the circuit 40.

  In the power supply circuit 5-1 having such a configuration, there is a photographing mode in which no problem occurs even if electromagnetic noise is generated by flowing an inductor current through the inductor 6. For example, when an image output from the image sensor 2 in a moving image state is displayed as a through image on an apparatus main body side liquid crystal display unit (not shown), and the user is thinking about the subject composition while looking at the through image on the liquid crystal display unit, There is no problem even if a little electromagnetic noise gets on the through image.

  In such a photographing mode, the circuit units 20 and 40 of the power supply circuit 5-1 in FIG. 1 are used to operate as a normal buck / boost step-up / step-down power supply circuit. Thereby, highly efficient and stable power conversion using the inductor 6 can be performed. At this time, the charge pump transistors 41 and 43 are short-circuited (maintained on), and the charge capacitor 45 is short-circuited.

  In the actual shooting mode, that is, in the shooting and recording mode, the user presses the shutter release button. As a result, analog captured image data is read from the image sensor 2, subjected to AFE processing by the analog front end (AFE), converted to digital data, and captured image data to the digital signal processor (DSP) on the apparatus main body side. Is output. Known image processing is performed on the apparatus main body side, and a captured image (a still image or a moving image) is stored in a recording medium. If electromagnetic noise occurs between the time when the release button is pressed and the digital data after AFE processing is converted, this electromagnetic noise affects the image quality of the captured image.

  Therefore, in the shooting mode in which electromagnetic noise due to the inductor 6 is desired to be avoided, the operation of the step-down switching circuit unit 20 is stopped, and instead, the linear regulator circuit unit 30 is made to perform a step-down operation. In other words, the output voltage of the battery 8 is switched to the step-down switching circuit unit 20 and is input to the step-up switching circuit unit 40 through the transistor 31 under constant voltage control. Thereby, generation | occurrence | production of the electromagnetic noise by the inductor 6 can be prevented.

  When this linear regulator circuit unit 30 is used, the operation of the step-up switching circuit unit 40 is switched depending on whether the output voltage of the battery 8 is high or low, and a desired output voltage of 3.3 V is obtained.

  Therefore, the output voltage of the battery 8 is detected by the input voltage detector 57. When the output voltage of the battery 8 is higher than a predetermined threshold voltage (for example, 3.5 V: a voltage capable of generating 3.3 V by only the subsequent step-down operation), the step-up operation is not necessary. The output of the linear regulator circuit unit 30 is directly output. That is, the controller 46 always turns on the charge pump switch transistors 43 and 44 and always turns off the transistors 41 and 42. As a result, the output of the linear regulator circuit unit 30 is directly input to the image sensor 2 through the output capacitor 51.

  When the output voltage of the battery 8 is low and boosting is required to obtain 3.3V, the boosting switching circuit unit 40 performs the boosting operation. At this time, by the combination of the linear regulator circuit unit 30 and the charge pump operation of the step-up switching circuit unit 40, the comparator 54 detects Vout / 2 to be the output of the linear regulator circuit unit 30, and the charge pump circuit 2 Double boosting operation is performed to obtain the desired 3.3V output.

  FIG. 2 is a flowchart showing an operation procedure of the power supply circuit 5-1 in FIG. First, in step S1, the input voltage input to the power supply circuit 5-1 is detected by the input voltage detector 57. Then, in the next step S2, it is determined whether or not the input voltage is equal to or higher than the threshold value (for example, 3.5 V). If the input voltage is less than the threshold voltage, the process proceeds to step S3, where the boost switching circuit unit 40 is enabled and the boost switching power supply using the inductor 6 is operated. That is, the transistors 43 and 41 necessary for the charge pump operation are fixed to the on state, and the boosting switching operation by the transistors 44 and 42 is performed.

  In the next step S4, a mode switching signal is detected, and it is determined whether or not there is a switching signal to a shooting mode for avoiding electromagnetic noise (step S5). The switching signal to the imaging mode for avoiding electromagnetic noise is issued, for example, from a CPU that is mounted on the camera module and controls the various controls of the camera module. If the result of determination in step S5 is that there is no signal for switching to the imaging mode for avoiding electromagnetic noise, the step-up switching circuit unit 40 is operated and the transistor 23 of the step-down switching circuit unit 20 is always turned on (step S6). . As a result, 3.3 V is generated and output by the step-up / step-down circuit of the circuit units 20 and 40.

  As a result of the determination in step S5, if it is determined that there is a signal for switching to the imaging mode for avoiding electromagnetic noise, the process proceeds to step S7, the linear regulator circuit unit 30 is set in the operating state, and the step-down switching circuit unit 20 is stopped. In step S8, 3.3 V is output without the inductor 6 by the charge pump operation of the linear regulator circuit unit 30 and the step-up switching circuit unit 40.

  If it is determined in step S2 that the input voltage is equal to or higher than the threshold voltage, the process proceeds to step S11, where the step-down switching circuit unit 20 is enabled and the operation of the step-up switching circuit unit 40 is turned off. That is, the transistors 43 and 44 connected in series with the output are fixed to the on state, and the transistors 41 and 42 are fixed to the off state.

  In the next step S12, a mode switching signal is detected, and it is determined whether or not there is a switching signal to a shooting mode for avoiding electromagnetic noise (step S13). If the result of this determination is that there is no switching signal to the imaging mode for avoiding electromagnetic noise, the step-down switching circuit unit 20 is operated (step S14), and 3.3V is generated and output.

  As a result of the determination in step S13, when it is determined that there is a signal for switching to the imaging mode for avoiding electromagnetic noise, the process proceeds to step S15, the linear regulator circuit unit 30 is set in the operating state and the step-down switching circuit unit 20 is stopped. In step S16, 3.3 V is generated and output by the operation of the linear regulator circuit unit 30.

  FIG. 3 is a circuit diagram of the power supply circuit 5-2 according to the second embodiment of the present invention. Circuit parts similar to those in the circuit diagram of FIG. 1 are given the same reference numerals and only different parts will be described.

  The power supply circuit 5-2 of the present embodiment provided between the battery 8 on the apparatus main body side and the image sensor 2 is provided with a charge pump type boosting switching circuit unit 40 that does not use an inductor on the front side (battery 8 side), A step-down switching circuit unit 20 is provided on the rear side (image sensor 2 side), and a linear regulator circuit unit 30 is provided in parallel with the step-down switching circuit unit 20.

  As in FIG. 1, the step-up switching circuit unit 40 includes transistors 41 to 44, a charge capacitor 45, and a controller 46, and a charge pump output capacitor (capacitor) 47 between the output line and ground.

  The step-down switching circuit unit 20 includes a comparator 54, divided resistors 52 and 53, and a reference voltage 55 similar to those in FIG. 1 in addition to the controller 21, transistors 22 and 23, and the inductor 6, but is different from FIG. Then, the comparison result of the comparator 54 is input to the controller 21.

  The linear regulator circuit unit 30 includes a transistor 31 and a controller 32, and the transistor 31 bypasses the output voltage of the step-up switching circuit unit 40 to the output capacitor 51. The drain output voltage of the transistor 31 is fed back to the controller 32.

  The mode controller 56 issues instructions to the controllers 46, 32, and 21 in response to the mode switching signal.

  In this embodiment, the step-down operation by the linear regulator circuit unit 30 is used so that current does not flow through the inductor 6 in a shooting mode that avoids electromagnetic noise, such as in a shooting recording mode. In an operation mode in which there is no problem even if there is an influence of electromagnetic noise, the step-down switching circuit unit 20 with high power conversion efficiency is operated to extend the life of the battery 8.

  FIG. 4 is a circuit diagram of a power supply circuit 5-3 according to the third embodiment of the present invention. In addition to the third embodiment of FIG. 3, a bypass switch 61 composed of a transistor controlled to be turned on and off by the mode controller 56 and the input voltage to the power supply circuit 5-3 are detected, and the detection result is sent to the mode controller 56. The difference is that an output input voltage detector 57 is provided.

  The transistor 61 is provided between the output line of the battery 8 and the output line of the step-up switching circuit unit 40, and is configured to short-circuit between the two in the on state. That is, when short-circuited, the output voltage of the battery 8 is directly applied to the inputs of the linear regulator circuit unit 30 and the step-down switching circuit unit 20.

  FIG. 5 is a flowchart showing an operation procedure of the power supply circuit 5-3 shown in FIG. First, in step S21, the input voltage input to the power supply circuit 5-3 is detected by the input voltage detector 57. Then, in the next step S22, it is determined whether or not the input voltage is equal to or higher than a threshold value (for example, 3.5V) used for switching operation between step-down operation and step-up operation necessary for outputting 3.3V. judge.

When the input voltage is less than the threshold voltage, it is necessary to boost the voltage. Therefore, in step S23, the boost switching circuit unit 40 is operated and applied to the inputs of the linear regulator circuit unit 30 and the step-down switching circuit unit 20, and the process proceeds to step S24. move on.
When the input voltage is equal to or higher than the threshold voltage, it is not necessary to boost the voltage. Therefore, in step S27, the bypass switching 61 is turned on, the boosting switching circuit unit 40 is stopped, and the linear regulator circuit unit 30 and the step-down switching circuit unit 20 are input. To step S24.

In step S24, a mode switching signal is detected. In step S25, it is determined whether there is a signal for switching to a shooting mode for avoiding electromagnetic noise.

  If the result of determination in step S <b> 25 is that there is no signal for switching to the imaging mode for avoiding electromagnetic noise, the step-down switching circuit unit 20 is also operated to output 3.3 V from the step-down switching circuit unit 20 to the image sensor 2.

If the result of determination in step S25 is that a signal for switching to a shooting mode for avoiding electromagnetic noise has been generated, the process proceeds from step S25 to step S28, where the linear regulator circuit unit 30 is turned on and the step-down switching circuit unit 20 is switched on. As the operation is turned off, 3.3 V is output from the linear regulator circuit unit 30 to the image sensor 2.

  As described above, in the present embodiment, in the operation mode in which electromagnetic noise avoidance is required, the energization of the inductor 6 is stopped and 3.3 V is generated, so that a high-quality subject image can be taken. Become. Further, when the output voltage of the battery 8 is high, the charge pump operation of the boosting switching circuit unit 40 is stopped and unnecessary boosting operation is not performed, so that noise associated with the switching operation of the transistor can be reduced, and charging by the boosting operation is further performed. The loss of the pump circuit can also be avoided, and the loss when the subsequent linear regulator circuit unit 30 is selected can be reduced.

  FIG. 6 is a circuit diagram of a power supply circuit 5-4 according to the fourth embodiment of the present invention. Compared to the power supply circuit 5-3 shown in FIG. 4, the only difference is that the bypass transistor 61 is omitted from the embodiment shown in FIG. 4.

  In the power supply circuit 5-4 of the fourth embodiment, instead of turning on the bypass transistor 61 of FIG. 4, the transistors 41 and 42 of the step-up switching circuit section 40 are always off and the transistors 43 and 44 are always on. The only difference is that the output voltage of the battery 8 is directly input to the input terminals of the linear regulator circuit unit 30 and the step-down switching circuit unit 20.

  As described above, the power supply circuit of the image sensor module according to the present embodiment includes the step-down circuit unit that steps down and outputs the input DC voltage using the switching transistor and the inductor, and the linear constant of the transistor provided in parallel with the step-down circuit unit. A linear regulator circuit unit that steps down and outputs an input DC voltage by a voltage operation, and is connected in series to a preceding stage or a subsequent stage of the step-down circuit unit, and the input DC voltage is changed by charge pump operation or switching between charge pump operation and step-up switching operation Boosting and outputting a boosting circuit unit, and stopping the operation of the step-down circuit unit during the photographing recording mode of the imaging device module and operating the linear regulator circuit unit to obtain a constant voltage necessary for driving the imaging device And a control control unit to be supplied to the element.

  Further, the power supply circuit of the image pickup device module according to the embodiment includes input voltage detection means for detecting an input DC voltage of the power supply circuit, and the control control unit is configured to output the boost circuit when the input DC voltage is equal to or higher than a threshold voltage. The step-up operation by the unit is stopped.

  Further, the power supply circuit of the image pickup device module according to the embodiment is characterized in that the booster circuit unit is connected in series to the subsequent stage of the step-down circuit unit.

  Further, in the power supply circuit of the image pickup device module according to the embodiment, when the input DC voltage of the power supply circuit in the photographing recording mode is less than a threshold voltage, the control control unit drives the image pickup device to the linear regulator circuit unit. A voltage that is ½ of a constant voltage necessary for the output is generated and output, and the input voltage is boosted twice by the booster circuit unit and output to the image sensor.

  Further, in the power supply circuit of the image pickup device module according to the embodiment, when the input DC voltage of the power supply circuit in the photographing recording mode is equal to or higher than a threshold voltage, the control control unit outputs the output of the linear regulator circuit portion to the image pickup device. And a constant voltage required for driving the image pickup circuit, and the boosting circuit section bypasses the constant voltage and outputs it to the image sensor.

  Further, the power supply circuit of the image pickup device module according to the embodiment is characterized in that the booster circuit unit is connected in series before the step-down circuit unit.

  The power supply circuit of the imaging device module according to the embodiment includes a switch circuit that bypasses the booster circuit unit, and the control control unit is in a short-circuit state when the input DC voltage of the power supply circuit is equal to or higher than a threshold voltage. The boosting operation by the boosting circuit unit is stopped.

  In the power supply circuit of the image sensor module according to the embodiment, the control control unit controls the operation of the booster circuit unit and inputs the booster circuit when the input DC voltage of the power supply circuit is equal to or higher than a threshold voltage. The input DC voltage is directly output from the booster circuit.

  In addition, an image sensor module according to the embodiment includes any one of the power supply circuits described above.

  According to the embodiment described above, the step-down operation using the inductor 6 is stopped and the step-down operation is performed by operating the linear regulator instead in the operation mode in which a high-quality image is taken as in the recording mode. Therefore, a high-quality subject image that avoids the influence of electromagnetic noise can be taken.

  The power supply circuit of the image sensor module according to the present invention avoids the generation of electromagnetic noise during a shooting mode in which the influence of electromagnetic noise affects the quality of a captured image, and generates a desired DC voltage. For example, it is useful when applied to an image sensor module mounted on a mobile phone or the like.

2 Image sensor 5, 5-1, 5-2, 5-3, 5-4 Power supply circuit 6 Inductor 8 serving as electromagnetic noise generation source Battery 20 on device side Step-down switching circuit unit 30 Linear regulator circuit unit 40 Step-up switching circuit 51 Output capacitor 58 Mode switching signal

Claims (5)

A power supply circuit for an image sensor module, a step-down circuit unit that steps down and outputs an input DC voltage by a switching transistor and an inductor, and a step-down input DC voltage that is provided in parallel with the step-down circuit unit by a linear constant voltage operation of the transistor A linear regulator circuit unit that outputs the output voltage, a booster circuit unit that is connected in series to the subsequent stage of the step-down circuit unit and boosts and outputs an input DC voltage by a charge pump operation, and the step-down circuit when the imaging element module is in a shooting recording mode A power supply circuit for an image sensor module, comprising: a control control unit that stops operation of the circuit unit and operates the linear regulator circuit unit to supply a constant voltage necessary for driving the image sensor to the image sensor.   The power supply circuit for the image pickup device module according to claim 1, further comprising an input voltage detection unit that detects an input DC voltage of the power supply circuit, wherein the control control unit is configured to detect when the input DC voltage is equal to or higher than a threshold voltage. A power supply circuit of the image sensor module for stopping the boosting operation by the boosting circuit unit. 3. The power supply circuit of the image pickup device module according to claim 1 , wherein when the input DC voltage of the power supply circuit in the photographing recording mode is less than a threshold voltage, the control control unit is connected to the linear regulator circuit unit. A power supply circuit for an image sensor module that generates and outputs a voltage that is ½ of a constant voltage necessary for driving the image sensor, and causes the boost circuit unit to boost the input voltage by a factor of two and output the voltage to the image sensor. . 3. The power supply circuit of the image pickup device module according to claim 1 , wherein when the input DC voltage of the power supply circuit in the photographing / recording mode is equal to or higher than a threshold voltage, the control controller is configured to control the linear regulator circuit. A power supply circuit of an image sensor module that causes an output to be a constant voltage necessary for driving the image sensor and causes the booster circuit unit to bypass the constant voltage and output the image sensor. Image sensor module having a power supply circuit according to any one of claims 1 to 4.

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